1. Field of the Invention
The invention relates to a filter dedusting arrangement in a vacuum cleaner.
2. Description of the Related Art
Such a filter dedusting arrangement is known for example from the subject-matter of DE 4138223 C1. The disclosure content of that publication is deemed to be embraced by the present invention.
In the cited publication, the change-over from the suction airflow to the extraneous airflow is made by an air supply duct which is translatable by means of a driving rod to optionally register with one or other of the two openings of the filter and put it in communication with the extraneous airflow, with an airtight connection.
Such an arrangement, however, has the drawback that the filter is not dedusted impulsively, but is merely dedusted by a steady inflow of extraneous air. Abrupt dedusting of the filter does not occur. Yet it has been found that an improved filter cleaning action can be obtained by impulsive, abrupt dedusting.
Therefore the fundamental problem of the invention is to develop a filter dedusting arrangement of the kind stated at the outset so as to produce a much better cleaning action.
The distinctive feature of the invention is that the secondary or extraneous airflow through the filter for dedusting is controlled so that by utilizing differences in pressure a flap element arranged in a casing abruptly changes its position and opens and/or closes one or more openings in the casing so that the secondary airflow impinges impulsively on the surface of the filter to be dedusted.
To that end, use is made of the pressure differences between the partial vacuum of the suction airflow and atmospheric pressure and/or a separately generated positive pressure.
The mechanism as a whole comprises a known filter made in at least two parts or two separate part-filters and a casing divided by partitions into several, preferably five, chambers.
When dedusting is initiated, secondary air in the form of ambient air or air under pressure is supplied via one or more valve devices to one chamber and to parts of the flap element. The latter is formed as a rotary vane, and is abruptly set in motion and pivoted from a first end position into a second end position where it closes a corresponding outlet-opening so that the secondary air admitted into this chamber impinges on the associated filter or filter-part (reverse side of filter) and supplies the filter with an airflow impulsively formed by the abrupt changeover of the flap element. In this way, the airflow impulsively directed on to the back of the filter is used to dislodge and blast away the dust particles present in the filter, thus producing an excellent cleaning action.
The flap element is preferably connected to other vane parts so that not only is it used to admit secondary air and thus to initiate the dedusting of the filter, but also other parts of the flap element serve to switch the suction airflow from the filter surface which is about to be dedusted to another, freshly dedusted, filter surface.
Thus the flap element has a dual function, viz.: first, that of abruptly or impulsively directing secondary air on to one filter surface with the aim of dedusting that filter surface, and second, that of directing suction air on to another, e.g. opposing, filter surface, which then performs the filtering function for which it is intended.
The two filter surfaces are interchangeable. On an alternating basis, one filter surface can be dedusted while the filter surface that is not undergoing dedusting serves as the filter surface proper, retaining the dust particles contained in the suction airflow.
This alternation of the opposing filter surfaces depends on when the flap element changes over.
The flap element is changed over by the admission of extraneous air through one of a number of inlet connections on the filter casing, by valve shutters shifted into their closed or open position by electric motor or electromagnet, or manually.
The changeover to dedust the filter surface by directing the extraneous airflow on to it can be electronically controlled by means of suitable sensors. In this case, the sensors detect e.g. the amount of soiling of the filter surfaces, and initiate dedusting of the soiled surfaces. Provision can of course be made for the dedusting operation to be initiated manually at any time.
What matters is that the flap element operates passively: that is to say, it does not have to be separately driven, but is simply pivoted into one or the other position by the difference in pressure between the suction airflow and the dedusting airflow in the vacuum cleaner.
In one possible embodiment, instead of using normal atmospheric air pressure alone for the dedusting airflow, a pulse of air under pressure is additionally introduced into this airflow; or, instead of the dedusting airflow from the atmosphere alone, a pulse of air under pressure is delivered to the filter surface for dedusting purposes.
The shape of the filter casing need not necessarily be cylindrical. Other filter geometries are also possible. For example, the filter may be rectangular, square or triangular, but it must be defined by the partitions which will be described presently and by the openings in the partitions.
Of course, be flap element must be adapted to the geometry of the filter casing.
Again, the filter surfaces need not necessarily be part of the filter casing. They may be connected to the filter casing by corresponding passageways and as a result may be made considerably larger, and with a larger surface area, compared to these which are described here in the embodiments.
The filter may for example be made relatively elongated in form, and the rotary vane for controlling the secondary air to be impulsively introduced may be arranged in the upper region of the filter, while the whole of the lower region of the filter is formed by corresponding filter surfaces.
Alternatively, one or more flat filters, impinged on by secondary air or suction air depending on the position of the flap element, may be used.
From this it follows that the switching part with the flap element can be spatially separate, or connected to a filter by its casing, the filter geometry being of secondary importance as previously stated.
In the illustrated embodiments, the filter casing itself comprises the filter surfaces involved in dedusting. This is shown only by way of example, and is not a necessary element of the solution.
All details and features disclosed in the documents, including the abstract, and in particular the configurative form shown in the drawings, are claimed as essential to the invention insofar as, taken separately or in combination, they are novel in relation to the state of the art.